I like them. It looks like you did a decent job of panning to keep the car fairly sharp (tough to really tell on my monitor here). I have two small suggestions for you:
1. I would zoom out a bit. I think that a car in motion is one time you don't necessarily want to fill the frame with the subject. If you leave a little more room in front of (or even behind) the car it adds context and helps the viewer feel the motion of the car. That is, you can tell it's moving by the background blur, so give the viewer a hint of where it's going (or from where it's speeding).
--This applies to (1) and (3) above. In (2), because the car is coming at you instead of across your field of view there is little to no motion blur to the background, just to the wheels. As such it could pass for a stationary shot, in which case filling the frame is perfectly appropriate.
2. I don't know if the course was sloped here (I suspect not by the vertical poles in the background), but if the angle of the car is solely due to camera tilt I would recommend tilting it the other way. A car is going to look faster if it's assumed to be speeding downhill rather than laboring uphill.